Our app-driven life: Smart-phone apps are becoming the north star for millions of Americans who use them to navigate through life – shopping, playing, reading, dating, learning, and more with their fingertips.

Worcester, Mass. — "There's an app for that" is more than just Apple's marketing mantra. Apps have become an American lifestyle.

"I'm using my phone when I'm sleeping," says Amanda Soloway. Every night, Ms. Soloway turns on an iPhone application called Sleep Cycle and tucks her smart phone into bed with her. The app monitors her sleep patterns and wakes her at the optimal moment – within a 30-minute time frame she has selected.

Before she's out from under the covers, she's checking the weather (another rainy day in Seattle) and connecting with her world via Facebook (photos from a dinner last night) and e-mail (some fellow University of Washington students want to push back today's meeting).

Once she's out the door, she plugs in her headphones and hunts for good walking music in SoundCloud. The jukebox app pulls up a few tracks from the DJ duo Poolside and streams them over her phone's cellular Internet connection.

As she dashes between classes for her master's in business administration program, Soloway's iPhone calendar app vibrates 10 minutes before important appointments.

She has more than 100 apps on her phone, each serving a different purpose. She deposits checks through the Bank of America app, finds bus schedules through OneBusAway, passes time playing Bejeweled, compiles grocery lists through ZipList, texts with her best friend through WhatsApp, and edits her photos with any of 18 different photography apps.

Soloway actually prefers regular computers. Websites never look quite right shining through a screen the size of a baseball card. Typing e-mails never quite feels right when she taps on the phone's smooth glass surface. But life extends well beyond the reach of her desktop.

"I remember when I got my iPhone," she says. "So many people told me, 'It will change your life.' But I was really hesitant. Now, I don't know if I could go back. My phone is just a lot more convenient."

Millions of Americans now rely on pocket-sized computers to shop, play, read, date, learn, work out, take photos, and find directions. These apps – shorthand for software applications – are the heart and soul of smart phones.

The app-driven life has kick-started a new computer revolution – one that has spread faster and become more intimate than any before.

The world has adopted smart phones and tablets 10 times faster than it embraced personal computers in the 1980s, twice as fast as it logged into the Internet boom of the '90s, and three times faster than it joined social networks in the new millennium, according to the app-tracking firm Flurry.

Svelte, intuitive hardware helps propel the movement, but this new era in consumer electronics really started a year after the debut of the original iPhone. In early 2008, Apple opened the digital doors to its App Store, an online marketplace for programmers around the world to sell their own mobile apps.

While Apple guarded the gates – demanding that each app be submitted for review – it kept a wide berth. Programmers for the iPhone and Google's competing Android line could take advantage of tools unavailable on most personal computers: touch screens, cameras, tilt sensors, compasses, location tracking, cellular Internet connections, and the fact that people carry these devices with them at all times.

Soon, apps emerged for practically every need in a person's day.

Productivity goosed by zombies?

Matthew Ablon uses his Android phone to keep fit. This freshman at Ouachita Baptist University in Arkadelphia, Ark., never liked running in high school. It seemed monotonous. Boring. A single app changed his mind.

This past semester, Mr. Ablon downloaded Zombies, Run! – a workout app that motivates people to run by appealing to their Darwinian desire not to get eaten by zombies. As Ablon runs, this run tracker mixes in elements of an audio adventure game. The app interrupts his normal music playlist with mission instructions – such as news that he's found (virtual) supplies that he can distribute to survivors living in a nearby (fictional) compound. But before he can return home with the provisions, he needs to pick up the pace and outrun the zombie horde.

This $8 app – quite a bit more expensive than the traditional 99-cent threshold for phone apps – is "worth every penny," says Ablon. He now runs two to three miles twice a week with imaginary zombies on his heels.

Is this a peculiar way to encourage good habits? Definitely. But is it effective? The British government thinks so. As the workout app rang up a quarter-million downloads, Britain's National Health Service commissioned the team behind Zombies to design a self-improvement app for the broader public (i.e., without the undead theme). The group plans to reveal this new project in the spring.

As apps worm their way into our daily lives, plenty of smart-phone owners now find the word "phone" becoming an increasingly anachronistic term for these devices. In a TIPP poll commissioned by The Christian Science Monitor, close to half of respondents (46 percent) reported using their smart phones more than 10 times a day for actions other than making a phone call.

"Apps bring out the human part of technology," says Scott Steinberg, a consultant and professional speaker on innovation in St. Louis. Desk-bound PCs were designed for business, he says. They're tools of productivity occasionally co-opted for entertainment. Yet while iPhone and Android owe a lot to BlackBerry (the pinstriped, business-minded older brother of the smart-phone family), apps were predominantly designed for life outside the office.

Apps replace scissors and glue

For a year and a half now, the Bancroft School in Worcester, Mass., has required each student from Grades 6 through 12 to own and carry an iPad. Apple's tablet computer plays a role in every class, says Elisa Heinricher, the administrator behind the private school's tablet program. Students dissect digital frogs for biology, read e-books in Spanish, and e-mail their English essays.

"The iPads have become such an integral part of our day that we don't even notice them anymore," says Ms. Heinricher.

In the four years since the App Store opened, Apple customers have downloaded 40 billion mobile apps; they downloaded 20 billion in 2012 alone.

This McDonald's-like number of customers served has caught some parents at the Bancroft School a bit off guard.

"My son had an assignment to create a collage," says Mary Ann Preskul-Ricca to a room of fellow Bancroft parents who meet with Heinricher once a month to keep on top of iPad trends and new apps. "Of course, I'm thinking, 'We need to get supplies and do we have glue?' He just says, 'No, Mom. There's an app.' " (The room laughs and there are several knowing nods.)

Ms. Preskul-Ricca is no Luddite. She uses an iPad regularly for work. "I'm a little slower at this stuff," she says after the meeting. "But it's just my generation. I grew up with paper and books."

On the other hand, eighth-grader Ashley Kiel seems pretty blasé about the new role iPads play in the classroom. She uses the tablet when it makes sense and sets it aside when the touch controls get in the way, such as when writing out math problems.

While Ashley and her classmates have never known middle-school life without tablet computers, Heinricher says the devices have transformed the school for the better. It removed the "sage on the stage" style of lecturing, empowering students to not only listen and absorb, but also see, touch, and create the lesson material. It's also cut down on textbook costs, wasteful paper use, and the weight of students' backpacks.

And according to a study commissioned by the Verizon Foundation, 39 percent of all American students in Grades 6 through 8 use a smart phone for homework; 31 percent use a tablet for homework.

A generation weaned on apps

Michael Nathanson wonders what the app landscape will look like when his 2-year-old son grows up. Already, Beckett is quite the smart-phone-savvy toddler.

When he was 6 months old, his parents read him the iPad versions of Dr. Seuss books. At 9 months, Beckett figured out how to slide his little finger across an iPhone, unlocking the device all on his own. After a year, he realized the phone was snapping photos of him, and started posing when his parents held up the device. By 18 months, Beckett talked to his grand-parents using Apple's FaceTime video chat, kissing the screen to say goodbye.

Smart phones and tablets "have just been such a part of his life that it's hard to imagine him knowing anything else," says Mr. Nathanson. "Like in the case of his grandparents, he knows that they're not there, but the screen is not a barrier for interacting with them."

Nathanson understands that screen time is no substitute for parenting. He and his wife have made sure to read Beckett paper books, buy him physical toys, and not to leave him with an iPhone unattended. Perhaps because of this sensitivity, Nathanson seems rather charmed by a recent shift in his son.

"At this point, he'd rather play with his train set than with the iPad," he says. Beckett still wants his dad to find videos of cars and trains on YouTube, but when it comes to playtime, toys win, hands down.

After hearing Beckett's story, child-development expert Nancy Darling lets out a cheer, but says that she's not really surprised by his new fascination. At that age, kids are very sensory oriented. They want reactions, smells, splashes, and clangs. Tablets and smart phones offer interactions, but only in a very limited way.

Because of this, the American Academy of Pediatrics recommends that kids under the age of 2 not get any screen time. This includes iPads, but Ms. Darling points out that the underlying research focuses on television, not tablets. Tablets are simply too new for studies to come down on one side or the other, says Darling, a psychology professor at Oberlin College in Oberlin, Ohio.

From her perspective, a tablet is more responsive than a TV or a book, "but it's nowhere near as interactive as a cat, or a ball falling down the stairs, or a mud puddle," she says.

Lawless app ecosystems?

When Beckett was born, Nathanson left his tech-industry job in San Francisco and moved across the country to Somerville, Mass., just north of Boston. Looking for a new project and perhaps a new career, he decided to teach himself how to program iPhone apps.

Nathanson was very involved in coding back at his old job, but knew little about Apple's programming language. As he dug in, Nathanson was surprised by how much control Apple had over the process – both directly and indirectly. He knew that Apple reviewed apps before they went online, but he didn't expect the company to foster a large library of half-finished code like little starter kits that give programmers a basic design but allow them to fill in the specifics and add in their own graphics.

This does more than ease the process for beginners, he says. It nudges developers to adopt Apple's vision of how apps should look and feel.

"Apple wants as much uniformity as possible," says Nathanson, who, as a first-time app developer, loved the simplicity. "This way, [iPhone owners] feel comfortable moving from one app to another. Android does that, too. When you read about best practices for app development, whether it be for Android or Apple or even Windows, they all say the same thing: Your app should not look the same on all three of these devices."

Soloway, the app-driven MBA student, says she's been tempted to turn in her iPhone for another device. Living in Seattle – Microsoft's backyard – many of her classmates preach the virtues of Windows phones. They are attractive, she admits, but switching seems like a waste of money.

"There's no reason to switch off of Apple because I've already purchased so many apps," she says. While her hundreds of iPhone apps work beautifully on an iPad, those downloads will not carry over to the Android or Windows Phone operating systems. In a way, these apps have locked Soloway into a single ecosystem. She uses apps from many different companies, but they all require the same single device.

"Part of me doesn't like the dependence on the one tool," says Sherry Turkle, author of "Alone Together: Why We Expect More from Technology and Less from Each Other." "Having my life concentrated on a single technology is very convenient and terrifying."

In this smart-phone age, Americans have become surprisingly casual with their privacy, says Ms. Turkle, an iPhone owner herself. When she grew up in the 1960s, people clung to their privacy – they politicized their privacy. They thought that no one should be able to read their mail – now companies provide free e-mail service in exchange for them being able to skim those in-boxes to serve up advertising. She wistfully remembers people objecting to surveillance programs – now apps such as Foursquare announce online that people have entered certain shops in exchange for discounts on that store's products. After Robert Bork's Supreme Court nomination in the late 1980s, Congress passed a law banning the publication of people's video rental history – now countless apps offer to automatically post even minute actions to a person's Facebook timeline.

"My generation – a very political generation, people in their 40s, 50s, 60s – have let their children down because we didn't help them think politically in terms of new technology," says Turkle. "We gave them these [smart phones] and said this is good for you; it will help you connect. And then we turned around and said, 'Oh, this is so shocking: They connect all of the time. Oh, how shocking: They don't care about privacy.' "

Of course, while privacy settings can seem nebulous, people do ultimately choose what to share online and how to broadcast that information. Still, Turkle says this moment of widespread self-surveillance – when people text, photograph, and geo-locate their daily lives – will come to a head with this generation of kids.

"Part of why I'm optimistic is that we don't have any laws for this," she says. "We're operating on rules that came before cellphones. There's a lot of conversation to be had, and I'm most interested in how we get that dialogue started."